Inflatable form for a concrete building



Den 8, 1965 w. w. BIRD ETAL INFLATABLE FORM FOR A CONCRETE BUILDING 7Sheets-Sheet 1 Original Filed July 22, 1960 pCOA/CRE TE L TER W6/R0,PETER A. ST/POBEL DR. PAUL Rowaveo andD/W/D w@uw%@ Dec. 28, 1965 w. w.BIRD ETAL INFLATABLE FORM FOR A CONCRETE BUILDING 7 Shee ts-Sheet 2Original Filed July 22, 1960 14444 TEE W. B/IQD, P5751? A. STROBEL, OR.PA u/ Ro/vs VED and 0/! Wu P. 24/1 1095 1366- 1965 w. w. BIRD ETALINFLATABLE FORM FOR A CONCRETE BUILDING Original Filed July 22, 1960 '7Shee ts-Sheet 5 H444 r51? WEIRD, PETER/4. STROBE'L D/a P401. A Ravel E0and DA V/D P. 2/! MORE Dec. 28, 1965 w. w. BIRD ETAL 3,225,413

INFLATABLE FORM FOR A CONCRETE BUILDING Original Filed July 22, 1960 7Shee ts-Sheet 4 @4 4, ro/ 3% W 1366- 1965 w. w. BIRD ETAL INFLATABLEFORM FOR CONCRETE BUILDING 7 Sheets-$heet 5 Original Filed July 22, 1960art OW 1444 L r51? WEI/P0, PE TERA. 571905.51, 0P. PAUL Pavel 0 and DAwe P. ZAMORE Dec. 28, 1965 w, w. BIRD ETAL 3,225,413

INFLATABLE FORM FOR A CONCRETE BUILDING Original Filed July 22, 1960 7Sheets-Sheet 6 01?. PAUL Roma v50 If and 0,4 m) 1. 2/? MORE 1386- 1965w. w. BIRD ETAL INFLATABLE FORM FOR A CONCRETE BUILDING 7 Sheets-Sheet'7 Original Filed July 22, 1960 I MORE W/u TE? #4 BIRD, P5 TERA.STROBE'L 01?. PAUL IPO/VGVt-D anaD/lV/D P. 2/1

United States Patent Original application July 22, 1960, Ser. No.44,645, new Patent No. 3,139,464, dated June 30, 1964. Divided and thisapplication June 25, 1964, Ser. No. 392,059 11 Claims. (Cl. 25-128) Thisapplication is a division of my copending application Serial No. 44,645filed July 22, 1960, which issued as US. Patent No. 3,139,464, datedJune 30, 1964.

This invention relates to improvements in building construction and morespecifically to means for utilizing inflatable envelopes in thefabrication of buildings of concrete or other building materials. In oneof its principal aspects, the invention relates to the use of aremovable, flexible, inflatable form in combination with a uniquestabilizing system comprising a structural member or members arranged insuch manner that the resulting structure is of improved stability forthe support of the poured or laid concrete.

A primary object of the present invention is, accordingly, to improvethe stability of inflated envelopes used in building construction.

Other objects of the present invention are to provide an improved formsystem for building concrete shell structures in order to greatly reducethe cost of the form work, and economical methods for producing suchconcrete shell structures.

Another object is to provide an improved form system, the components ofwhich are readily portable and reusable.

Another object of the invention is to provide an improved air-supportedform for concrete work which will be of improved versatility anddependability.

Other objects and advantages of the invention will appear from thedetailed description hereinbelow, and the accompanying drawings.

The use of inflatable forms has heretofore been largely limited toessentially spherically-shaped structures, as only such shapes providesuflicient stability to acceptably support the weight of concrete duringforming. Also, the inflation pressure required to support the weight ofwet concrete results in much higher fabric loads with prior artarrangements, and has therefore heretofore necessitated use of heavy andrelatively costly fabric materials; thus making the form costsprohibitive, especially for larger size structures.

Air inflated members inherently tend to assume generally circularcross-sectional shapes, as this form represents an equilibriumcondition. In a spherical structure all elements are circular and thepressure is therefore resisted by equal tension in all circularelements. Distortion of a spherical shape under non-uniform loading isrelatively small as the load is at least partially redistributed betweendifferent circular elements to achieve an equilibrium condition withoutexcessive distortion. With a cylindrical shape the inflation pressure isresisted by hoop tension in the circular elements, while the pressureagainst the ends of the cylinder is resisted by tension in thelongitudinal direction. Under a uniform loading this shape is relativelystable, but under a non-uniform loading, such as would be encountered insupporting wet concrete, or under wind loads, the shape immediatelydistorts because on a cylindrical section non-uniform loads canbesupported only by distortion, as this is the only way in whichequilibrium conditions can be established at every point on the surface.Thus, if such distortion is not limited, the shape of the form willchange upon placement of the concrete, and also it may shift under windloads before the concrete is set. Obviously, a distortable form is notsuitable for use with concrete because such forms cannot maintain therequired shape and the supported concrete will be subject to crackingduring setting. It is because of such factors that use of the inflatableforms for supporting wet concrete has heretofore been practical onlywith essentially spherically shaped structures.

The present invention in its principal embodiments contemplates use ofair-supported forms of flexible sheet materials, in combination withprefabricated structural members formed from lightweight structuralelements in a manner such that the inflation pressure stabilizes andpro-stresses the trusses which in turn serve to shape the inflatableform. The form is patterned so as to provide a shell form surface havinga general curvature and comprising a plurality of subsidiary arch shapedportions, thereby limiting the fabric loads to relatively small values;thus permitting use of higher inflation pressures such as are requiredto properly support the weight for example of wet concrete. Thestructural trusses may become integral parts of the resulting reenforcedconcrete beams formed after placement of the concrete.

Exemplary forms of the invention are illustrated in the drawingfurnished herewithin wherein:

FIG. 1 is a perspective view of a frame-stabilized airsupported formconstructed in accordance with the present invention;

FIG. 2 is a section through the inflated form along lines IIII of FIG.1, illustrating the distribution of inflation pressure loads;

FIG. 3 is a section through one of the trusses taken on line III-III ofFIG. 2, showing the loading thereon;

FIG. 4 is a fragmentary side elevational view of one of the structuraltruss members illustrating the loading of the arch by inflationpressure;

FIG. 5 is a section through the form taken along line VV in FIG. 1,ilustrating in more detail the shape and arrangement of the components,and showing concrete in place;

FIG. 6 is an enlarged detailed view of a portion of FIG. 5;

FIG. 7 is a fragmentary perspective view on enlarged scale showing theform and concrete structure at the base of the arch;

FIGS. 8, 9 and 10 illustrate sequential steps of one method of erectingthe form;

FIG. 11 is a fragmentary section through an end supporting beamillustrating a method of joining the beam to the form and anchoring itto ground;

FIG. 12 is a section on line XIIXII of FIG. 11 illustrating details ofthe attachment of the form to a supporting beam;

FIG. 13 is a section through a typical finished concrete archconstructed inaccordance with the invention;

FIG. 14 is a fragmentary section corresponding to FIG. 6 but of amodified form of the construction;

FIG. 15 is a view also corresponding to FIGS. 6 and 14 but showing asupplementary deviceof the invention; FIG. 16 is a section taken on lineXVI-XVI of FIG. 15;

FIG. 17 is a perspective View of a frame-stabilized airsupported formsimilar to that shown in FIG. 1, but having a spherically shaped endsection;

FIG. 18 is a perspective view illustrating the frame and form for ahemispherically-shaped building;

FIG. 19 is a fragmentary perspective view illustrating the use oftransverse stiflene'rs;

.tural .trusses 22 as shown inFIG. 3.

FIG. 20 is a section on enlarged scale thru the form taken along lineXXXX of FIG. 19, illustrating the position of the transverse stiffenerand showing the concrete in place; and

FIG. 21 is a section thru the transverse stiffener taken along lineXXIXXI in FIG. 20.

As shown herein by way of example, one form of the present invention asillustrated in FIG. 1 may be constructed to comprise a fabric envelope20 made of substantially airtight pliable material, such as a coatedfabric or plastic film or the like. The envelope is patterned and joinedto form barrel-shaped arch sections as indicated at 21 in FIGS. 1, 2 and10. One or more structural truss members 22 are placed in the valleysformed by the barrel arch sections, and are anchored at their ends intothe foundation 23. The shape of the form and relationship between thestructural arches 22 and fabric envelope 20 is shown in FIG. which showsthe form and concrete shell 38. The form 20 is patterned to provide thedesired radius of curvature and is provided with load cables 45 runningthe length of each valley and fixed to the envelope 20 by means ofstrips 46. These cables 45 are used to define the barrel-shaped archsections and position the form 20 prior to placement and attachment ofthe structural trusses to the envelope. End panels 24 close off the endsof the form 20 to provide an essentially airtight enclosure. In order tosupport the relatively high inflation pressures required, and to preventdistortion of the form envelope 20, the end panels are reinforced as bybeams 26, which are stabilized by tying together opposing beams atopposite ends of the envelope as by means of cables 27; or the panelsmay be otherwise stablized to resist the pressure loads. The side andend walls are each equipped with seal skirt portions 29 whichlay on theground (or on a seal diaphragm, if necessary) to provide a reasonablyairtight enclosure. In order to shape and position the outer side of theend barrel arch sections C of the form, cables 32 are bonded into eachend panel and are joined to anchors 34 at each end.

When the form 20 is inflated and the structural trusses 22 are in placeand are anchored at their ends to the foundation 23, it assumes theshape approximately as illustrated in FIG. 2. Inflation pressure actingas indicated by arrows in FIG. 2 tensions the barrel arch sections 21 ofthe form, drawing them up around the struc- As graphically illustratedin FIG. 4, the fabric tension (arrows 42) in the form envelope .isresisted by tension (arrows 43) in the slender truss members. Thispretensioning of the trusses increases their resistances to bending andcompressive loads, and also ultimately increases the structuralefficiency of the reinforced concrete rib 25 which is formed therearoundand of which the truss may become a part. The trusses 22 are designed sothat when they are pretensioned and stabilized by the form 20 they willbe capable of supporting in bending the unbalanced loads due toprogressive placement of wet concrete, as well as any aerodynamic loadsthereon due to wind gusts, etc. Guys as indicated at 44 (FIG. 4) may beemployed if desired interiorly of the form to further stabilize the formtrusses.

FIG. 6 illustrates the general details of one means for the attachmentof the trusses 22 to the fabric 20, and additional stabilizing means.Chairs 62 are used to position the trusses 22 in spaced relation to thefabric form 20. Means such as studs 76 are fastened at intervals alongthe arch for the purpose of attaching the trusses to the fabric form andto secure the tie cables 64 which space and position the trusses toresist the spreading loads developed during placement of the concreteover the barrel arch sections. The tie cables 64 are joined to the studs76 by means of attachment plates 68, which are bored to fit over thestuds 76. In order to assure a snug, substantially airtight connectionthrough the form, seal rings 63 which fit tight against the studs andare squeezed between the platets 68 and chairs 62 are clamped and heldin position by means of locking clips 70 which slip into grooves formedin the studs 76. To facilitate removal of the fabric form from thefinished concrete structure, cords as indicated at 71 are convenientlyfixed to the clips 70. Concrete reeinforcing mesh as indicated at 72 mayof course be strategically placed, as is well known in the art. I

FIG. 7 shows a detail of one means of terminating the concrete archsections at the side walls. In this arrangement footings are provided ofa construction suitable to support the weight of the final structure andto provide suflicient resistance to the uploads due to inflation pressure. Cross ties 82 may be used to react the side thrust from the archmembers when soil conditions require. Vertical side walls 84 areprovided in order to terminate the concrete arch sections. In setting upthe form, the cables 45 are attached to the foundation by using anadjustable attachment means such as the turnbuckles 86 and anchor bolts87. These cables form valleys in the envelope When inflated and supportand position the structural arches prior to attachments thereof to thefoundation 80. The barrel arch sections of the form 20 terminate againstthe side wall 84. An arch shaped angle frame 90, which is made to thecontour of the barrel arch intersection at the side wall, is clamped upagainst the side Wall to hold the form material securely against theside wall, such as by means of clamps and bolts 92. When the form'hasbeen'inflated and the arches are lifted up into place, attachments ofthe trusses to the foundation are made by means of anchor rods 94provided to extend from the foundation for connection to the trusses bywelded or bolted connections as indicated at 96. When these connectionsare completed, the tensioning on cables 45 are released by slackeningoff turnbuckles 86, which then allows the pressure to be transferred tothe structural arches 22, pretensioning and stabilizing them inpreparation for placement of the concrete.

While the inflated form 20 may be erected and positioned prior toplacement of the structural arches, which can then be installed by usinga crane to lift them up into place, if preferred, the inflated form 20can be used as a means for lifting the trusses into place without theneed for cranes or other heavy equipment. Such an erection technique isillustrated in FIGS. 8l2. Here it will be noted that the inflatable formis laid out and the cable attachments made to the base as previouslydescribed and shown in FIG. 7. The end panels are laid out and thepositions of the base of each end beam 26 located and staked down asillustrated in FIG. 11. The anchors 34 for attachment of cables 32 areinstalled and these cables are attached. The beams 26 are then laid inposition on the fabric form and are attached to cable 32 (see FIGS. 11and 12) by means such as a U bolt 100. In order to position the endpanels of the form on the beams, the panel is clipped to the beamsperiodically along their lengths, by means such as hooks 102 welded tothe face of the beam, and grommets 104 are inserted into the fabricform. In order to provide a good air seal, soft rubber washers 106 areused at the hooks so that the tension in the fabric and inflationpressure would Press the grommets down against the cushions wheninflated. In order to fix the base of the end beams 26 in the properlocation, swing links 108 are attached to the base of the beams andstakes 110 are driven i t {1'1 ground on each side of the beam. Thisarrangement allows the beam to fold down as illustrated in FIG. 8, yetguides it during inflation into the proper vertical position.

When the form fabric 20 is laid out and securely anchored around thesides by means of cables 45 (FIG. 7) and with the end beams in place,the structural trusses 22 are laid across the form so that they can thenbe lifted into position without the use of a crane by inflating theform. In order to do this, the fabric is drawn out toward one end, asfar as possible. The second from the end truss 22 is laid across theform and attachment is made to the positioning stud-s 76 as shown onFIG. 6. In making this attachment, seal ring 63 is put in place and thecable attachment plate 68, and locking clip 70 are used to securelyanchor the truss to the form. With the fabric deflated, such attachmentto the form is made only along approximately the upper /3 of the arch.The other three trusses are laid up in overlapping position asillustrated in FIG. 8 and attached to the form in a similar manner. Asthe form is inflated it would rise as sequentially illustrated in FIGS.8-10. Guy ropes 112 are used to stabilize the excessive billowing. Whenpressure is applied it starts to lift the end beams first. The sequenceof erection is controlled by maintaining weight on the lower beams untilthe upper beams have been raised to the desired position. As the form isinflated, the end sections of the structural trusses are swung down intothe valleys formed by tension developed on cables 45. The entireassembly is then positioned and stabilized by means of guy wires 112,and the remaining attachment of the envelope to the trusses by means ofstuds 76 is now conveniently completed.

The form is maintained inflated at relatively low pressure (such as froml"-2" water column) to position and support the structural trusses 22while they are being attached at their ends to the footings 80. Whenthis attachment has been completed, the form cables 45 are loosened,allowing the form to press up against the chairs 62 used to space thetrusses up off the form fabric. As the inflation pressure is increasedto a value suflicient to support the weight of concrete to be applied,the form pre-tensions the light structural members of the truss aspreviously described, thus increasing the bending resistance of thetruss so that it acts to resist bending distortion due to non-uniformloading under the weight of concrete and due to wind loads.

The concrete is so placed as to first build up the valley sections tocombine with the trusses to form beam sections. Concrete is placedeither by pouring or by gun. The sequence of the concrete placement ispreferably planned so as to minimize the bending deflection of the form,prevent cracking in the fresh concrete and to give better compaction;such as by starting at the opposite lower ends and working up. Thus,concrete is first placed for each beam as indicated at 50 (FIG. 13) andis allowed .to develop its initial set and strength before placing theconcrete in' the intermediate arch sections as indicated at 52. Thisinsures that the reinforced concrete O beams so produced are ofsufficient strength to maintain their relative positions while theconcrete for the intermediate arch section is being poured and hasdeveloped its initial set. The arch sections are placed in similarmanner, by spraying or by laying the concrete as uniformly as possiblewith any suitable equipment. Reenforcing mesh can be used in theconcrete shell as required by structural considerations. The form iskept inflated until the concrete has developed sufiicient strength to beself supporting. The form is then removed, and any subsequent treatmentof the concrete may be applied as required.

In order to form buildings of a length longer than that provided by thesingle form, after one section of the building has been formed and set,the form is easily re moved by releasing the clips 70 and deflating andlowering the forms to the ground. The form is then relocated to form anew section of arches, placing the form so that the end form sectionlies under the last concrete arch in order to lock the form to theprevious shell and maintain proper alignment. The process may berepeated to provide successive shell sections.

It should be recognized that the details illustrated up to this pointare of but one form of this invention. The structural truss 22 may be ofa variety of shapes and construction as best suits the particularbuilding design. Likewise, the design of the form at the ends, and theprovision for attachment to the form, can vary in detail, the importantconsideration being only that the ends of the form be restrained so asto resist pressure loads and to maintain the prescribed shape of theform.

Whereas the drawing and description up to this point illustrates theinvention by way of example in a construction wherein the structuraltrusses are ultimately embodied in the beam sections of the pouredconcrete shell structure, it is to be understood that the trusses may beotherwise arranged to provide the requisite stabilizing support for theinflated envelope during the wet concrete support phase of theoperation. For example, the trusses may be disposed interiorly of theenvelope fabric instead of exteriorly thereof, and tied thereto bysuitable devices to provide the valley formations in the envelope wheninflated as shown in FIG. 14. In this case the support truss does notbecome an integral part of the concrete structure, and the latter istherefore preferably reinforced by suitably placed reinforcing rod-s 114and/or reinforcing mesh as indicated at 7-2. Again, in such case thebeam sections are preferably poured first and allowed to set up toprovide rigid arch beam sections prior to placement of concrete on theform fabric intermediately of the beams, as explained hereinabove. Forexample, as shown in FIG. 14 the trusses can be constructed as indicatedat 116 to include top plates 118 carrying clamp flanges 119. Detachablelocking plates 120 are arranged to be connected to the flanges 119 as bymeans of bolts 122, whereby the truss 116 may be gripped upon the cable45 hereinabove referred to.

FIGS. 15, 16 illustrate an accessory device that can be usefully appliedin conjunction with the system of the present invention to provideimproved stability of the arch sections and control of the surface formof the inside of the concrete shell when finished. As shown therein,pluralities of panels can be loosely placed in any desired patternarrangement on top of the envelope fabric to supplement the latter indetermining the local surface texture of the finished concrete. Forexample, the panels 125 can be surface-embossed or curved or otherwisegeometrically shaped so as to present to the wet concrete being pouredthe desired form surface; it being understood that the panels 125 are inany case supported by the fabric envelope in operative position withoutneed for any complicated attachment devices. FIG. 16 specificallyillustrates a typical corrugated panel type such as can be used toproduce a corrugated surface texture as explained hereinabove. It willbe apparent that the panels 125 also cooperate to further stabilize thearch sections of the forms and prevent local distortions of the formsurface, in addition to shaping the ceiling surface of the concreteshell. Such panels, or other pieces, can either lie removed when theform is deflated, or are arranged to be embedded in place in thefinished concrete to become an integral ornamental surface portion ofthe concrete shell.

FIG. 17 corresponds to FIG. 1 but illustrates another form of buildingconstruction that can be fabricated in accordance with the presentinvention. In this case the ends of the building are of generallyhemispherical shape and include pluralities of trusses (which aregenerally of the type of the girthwise trusses 22) extending radiallyfrom a central top connection point 132. Thus, in the case of FIG. 17 nostiffening beams such as indicated at 26 (FIG. 1) are required inconnection with the flexible form fabric to stabilize it during theconcrete pouring operation. FIG. 18 illustrates a full hemisphericalshaped building constructed in accordance with the invention wherein thefabric envelope material is stabilized by trusses 130 and is therebycaused to assume the secondary arch configurations 21 as explainedhereinabove. Thus, subsequent placement of concrete over this formresults in the fabrication of a complementaryshaped shell-form concretestructure which integrally incorporates the reinforcing truss components130.

FIGS. 19, 20, 21 illustrate still another modification of the formstructure as illustrated and described hereinabove, wherein arch-shapedtransverse stiffeners 134 are disposed at intervals transversely of thesecondary arch sections 21 to extend between the trusses 22. By reasonof this arrangement the fabric between the trusses 22 is furtherstabilized at appropriate intervals by the stiffeners 134, and thelatter also act to relatively stabilize the trusses in their prescribedspaced relationships, and otherwise generally reinforce the envelopestabilizing system.

It will of course be appreciated that although only a few forms anddetails of the invention have been illustrated and described in detail,various changes may be made therein without departing from the spirit ofthe invention or the scope of the appended claims. For example, thebuilding material placed on the form 20 need not be in settable form. Inlieu thereof pre-cast concrete slabs might be used.

We claim:

1. A form for a concrete building comprising, in combination,

an inflated envelope marginally contacting a supporting surface andarching thereover, series of flexible tension devices anchored at theiropposite ends to the supporting surface connected to the inner surfaceof said envelope and disposed therewithin, said tension devices beingdisposed in spaced, generally parallel relation to providelongitudinally spaced and transversely extending corrugations in thesurface of said envelope,

a series of external truss members disposed within the valleys of saidcorrugations and substantially coextensive therewith, connector meansdisposed in longitudinally spaced relation on each truss member andprojecting through said envelope into the interior thereof,

and flexible tension means connecting the connector means of adjacenttruss members to maintain spacing therebetween in accord with thespacing between adjacent valleys of said corrugations.

2. The form according to claim 1 wherein said connector means comprisepins fixed to said truss members, a plate received on each pin, and aremovable clip retaining each plate on its associated pin.

3. The form according to claim 2 including a grommet between each plateand the inner surface of said envelope.

4. The form according to claim 1 including a flexible strip secured tothe inner surface of said envelope along each corrugation valley thereofand forming a tunnel with such inner surface, the first mentionedflexible tension members being received in such tunnels.

5. A concrete building form comprising, in combination,

an inflated envelope of transversely corrugated form,

a series of external truss members disposed in the val leys of saidcorrugations and including connector means projecting through saidenvelope and into the interior thereof,

and flexible connector tension means connecting the connector means ofadjacent truss members to maintain spacing therebetween in accord withthe spacing between adjacent valleys of said corrugations.

6. The form according to claim 5 wherein said connector means comprisepins fixed to said truss members, a plate received on each pin, and aremovable clip retaining each plate on its associated pin.

7. The form according to claim 5 including a grommet between each plateand the inner surface of said envelope.

8. A concrete building form comprising, in combination,

a base member having a pair of spaced, upstanding sidewalls,

an inflated envelope arching between said side walls and secured to theinner faces thereof, a series of flexible tension members secured atopposite ends to said base member adjacent said side walls and connectedto the interior of said envelope to form corrugations therein, series ofexternal truss members arching between said side walls in the valleys ofsaid corrugations,

and means disposed interiorly of said envelope staying said trussmembers against displacement from said valleys.

9. The form according to claim 8 wherein said means comprises connectorpins on said truss members projecting through said envelope, platemembers removably secured to said pins interiorly of said envelope, andguy wires connecting plates of adjacent truss members.

10. The form according to claim 9 including grommets around said pinsbetween said plates and the inner surface of said envelope.

11. The form according to claim 10 including a flexible strip secured tothe inner surface of said envelope along each corrugation valley thereofand forming a tunnel with such inner surface, said flexible tensionmembers being received in such tunnels.

References Cited by the Examiner UNITED STATES PATENTS 2,270,229 1/ 1942Neff 25-128 2,324,554 7/1943 Billner 25-128 2,616,149 11/1952 Waller50-52 2,624,931 1/1953 Billner 25-128 2,812,769 11/1957 Schaefer et al.50-52 2,948,047 8/1960 Peeler et al. 25-128 WILLIAM J. STEPHENSON,Primary Examiner.

' MICHAEL V. BRINDISI, Examiner.

5. A CONCRETE BUILDING FROM COMPRISING, IN COMBINATION, AN INFLATEDEVELOPE OF TRANSVERSELY CORRUGATED FORM, A SERIES OF EXTERNAL TRUSSMEMBERS DISPOSED IN THE VALLEYS OF SAID CORRUGATIONS AND INCLUDINGCONNECTOR MEANS PROJECTING THROUGH SAID ENVELOPE AND INTO THE INTERIORTHEREOF, AND FLEXIBLE CONNECTOR TENSION MEANS CONNECTING THE CONNECTORMEANS OF ADJACENT TRUSS MEMBERS TO MAINTAIN SPACING THEREBETWEEN INCCORD WITH THE SPACING BETWEEN ADJACENT VALLEYS OF SAID CORRUGATIONS.